1. Field of the Invention
The present invention relates to power distribution networks that use capacitance to compensate for inductive loads on the power distribution lines.
2. Description of the Related Art
Power distribution networks are used to distribute power to a plurality of residential or commercial customers. Typically, such networks involve voltage waveforms which are phase-shifted by approximately 120 degrees to establish three voltage phases (i.e., the A phase, the B phase, and the C phase). For a more detailed description of such power distribution systems, see U.S. application Ser. No. 08/012,280, entitled "Substation Load Distribution Monitor System," filed Feb. 1, 1993, now U.S. Pat. No. 5,406,495. Among the problems observed in typical power distribution networks, one prevalent problem is the inefficiency of power distribution caused by inductive loads on the distribution lines.
In order to compensate for inefficiencies due to inductive loads on the power distribution lines, a number of switched capacitors are utilized within the power distribution system. As is well known in the art, capacitance compensates for phase shift, reduced voltage and other undesirable effects of inductive loads. Thus, electric utility companies typically utilize capacitors to improve the efficiency of their electrical distribution systems. Capacitors utilized by electric utility companies may be permanently active (that is, permanently connected to a power distribution line) or may be switched on- and off-line by some control or command operated device. Permanently active capacitors are typically called "fixed capacitors," while controllable capacitors are typically called "switched capacitors."
In typical power distribution systems, a number of power distribution lines branch from the main system via substations. One or more switched capacitors may be configured to connect or disconnect from a given power distribution line associated with a particular substation.
Commonly, distribution lines within an electrical distribution system are reconfigured constantly in order to meet power requirements on any given day. Thus, a particular switched capacitor can be part of a distribution line under the control of one substation on one day, and part of another distribution line under the control of the same or another substation on another day. Capacitor reconfiguration is often performed by an in-field technician, who does not record that a capacitor within a substation control group has been reconfigured. Capacitors which are reconfigured without notification to the appropriate substation controllers are called "lost capacitors." These lost capacitors may be assigned to one distribution line of one substation while actually being configured into another distribution line of the same or another substation. Thus, when the capacitor is switched, it affects the wrong distribution line.
In addition to the above-mentioned limitations, since a lost capacitor causes no change in the state of the distribution line connected to the substation to which the lost capacitor is assigned (i.e., because it is no longer a part of the assigned distribution line), it is difficult to determine if the capacitor is defective, or has simply been reconfigured. Thus, it is important to determine the electrical location of reconfigured capacitors in order to properly regulate loads in a power distribution network.